- some sanitizing of sector tag/line id management:

* make setting the line ID with P_TranslateLineDef explicit because there's one FraggleScript function that needs to work around the changes caused by this. There's also some functions setting only a temporary linedef. These would inevitably cause problems if the underlying data gets changed.
* remove FS function 'ChangeTag'. Fortunately this was just some long forgotten test stuff that can be removed without affecting any maps, but the feature would cause some serious problems in a more complex system.

With these changes it is guaranteed that after map setup the tag/ids won't change anymore.

src/thingdef/thingdef_codeptr.cpp

@@ -70,6 +70,7 @@
 #include "m_bbox.h"
 #include "r_data/r_translate.h"
 #include "p_trace.h"
+#include "p_setup.h"
 #include "gstrings.h"
 
 
@@ -4506,7 +4507,6 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_Weave)
 //===========================================================================
 
 
-void P_TranslateLineDef (line_t *ld, maplinedef_t *mld);
 DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_LineEffect)
 {
 	ACTION_PARAM_START(2);
@@ -4520,7 +4520,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_LineEffect)
 		if ((oldjunk.special = special))					// Linedef type
 		{
 			oldjunk.tag = tag;								// Sector tag for linedef
-			P_TranslateLineDef(&junk, &oldjunk);			// Turn into native type
+			P_TranslateLineDef(&junk, &oldjunk, false);			// Turn into native type
 			res = !!P_ExecuteSpecial(junk.special, NULL, self, false, junk.args[0], 
 				junk.args[1], junk.args[2], junk.args[3], junk.args[4]); 
 			if (res && !(junk.flags & ML_REPEAT_SPECIAL))	// If only once,